Ascorbic acid, or vitamin C, aids in many functions of the body, including the absorption of iron. Large doses of C do not usually cause toxicity because, as a water-soluble vitamin, it is simply excreted in the urine. People who tend to form kidney stones may find their condition aggravated by vitamin C supplementation or megadosing.
A.D.A.M. Editorial Team: David Zieve, MD, MHA, and David R. Eltz. Previously reviewed by Alison Evert, MS, RD, CDE, Nutritionist, University of Washington Medical Center Diabetes Care Center, Seattle, Washington (2/15/2011).